Westinghouse has recently completed the evaluation and optimization of nuclear fuel cycles for both 18-month (520 EFPD) and 24-month (700 EFPD) fuel cycle lengths in high power density Westinghouse plants with 17 × 17 fuel, including enrichments and burnup above the current licensed limits. Westinghouse has developed a comprehensive levelized cost of electricity (LCOE) methodology to compare the different fuel cycle and plant operational scenarios on an equivalent net present value basis. This method realistically accounts for the expenses related to fuel procurement, manufacturing, in-core utilization and disposal as well as the plant operational aspects of outage cost and site staffing, capital expense, construction recovery, major modifications, uprates and load follow.
The resulting LCOE gives a single figure merit allowing comparison of scenarios on a consistent basis to evaluate potential economic benefits of various fuel and plant operational options. These options include the use of Intermediate Enriched Uranium (IEU), various fuel cycle lengths, pre-operational interest, incore carrying charges, used fuel storage, used fuel disposal, plant operations, plant capitalization, maintenance, outages, replacement power, generation revenue, capital improvement, licensing transition costs, uranium transition costs and others are explicitly accounted and discounted back to a common reference time irrespective of the fuel cycle length or plant design options with higher 235U enrichment and discharge burnup than the current prevalent fuel designs. Where appropriate, assumptions have also been made to incorporate reactor operational and other cost aspects.
This paper presents the methodology used to evaluate the LCOE of a power reactor that is independent of the reactor design and applies that methodology to sample fuel management cases of arbitrary fuel cycle length. These evaluations make a number of conclusions that are dependent on the power density of the plant. In general, many nuclear power plants operating within reasonable US cost models are generally at minimum LCOE when operated on 24-month cycles within the current licensing regime of peak rod burnup < 62 GWD/TU and fuel enrichment < 5 w/o 235U, hereafter referred to as “LEU”. The exception to this conclusion comes for the high-power density 17 × 17 Westinghouse units where the current licensing regime of 18-month LEU fuel cycles results in minimum LCOE thereby making cycle length extension to 24 month cycles economically unattractive with the current fuel products. The reason is that these Westinghouse plants, when operating on 24-month cycles, require feed batch fractions well above 50% of the core loading resulting in low fuel utilization and steep fuel cycle cost penalties that cannot be compensated by operating cost savings or additional generation revenue arising from 24-month cycle operation.
Westinghouse has explored scenarios where the current licensing regime restrictions on enrichment and burnup are removed and has found that, when Intermediate Enriched Uranium (IEU) (5 w/o 235U < IEU < 20 w/o 235U) and high burnup (HBU) in which lead rod burnup in the range of 75 GWD/TU are allowed, the optimal cycle length for these Westinghouse plants changes from 18-months to 24-months. This conclusion holds true over a wide range of input economic assumptions. Westinghouse has also evaluated 18-month cycles for Westinghouse units using current enrichment and burnup licensing paradigm and for the case where IEU is enabled and HBU is licensed. Westinghouse concludes that the IEU and HBU for 18-month cycle option for Westinghouse units results in a significant penalty when compared to both the 24-month HBU, which is the most economical, and the 18-month cycle under the LEU paradigm.